As an improvement over the spray painting of articles such as automobile bodies, boats and household appliances, a new kind of paint-coated sheet material or film has been developed to provide protective and decorative finishes. The new material comprises a flexible, stretchable, thermoplastic support sheet, also known as a carrier film, which has on one side a paint layer, also called a basecoat, of uniform thickness and appearance and, optionally, on the other side an adhesive layer. It can also have other layers such as a tie or bonding layer between the paint layer and the carrier film. In a preferred embodiment a transparent topcoat, also called a clearcoat, covers the paint layer. This combination provides an attractive basecoat-clearcoat or clear-over-color appearance.
Using known thermoforming procedures such as vacuum forming and in-mold bonding, preferred types of the paint-coated sheet material can be stretched and bonded to automobile body panels or other articles to provide a basecoat-clearcoat finish. Advantages over obtaining such finishes by spray painting include economy in the use of paint and improved control of evaporating solvents, which reduces air pollution. Furthermore, the new material has a remarkably smoother and more attractive appearance than spray painted finishes.
The new type of thermoformable sheet material and a process for its manufacture are described in the U.S. patent application of G. G. Reafler Ser. No. 116,426, filed Nov. 3, 1987 now abandoned. The process involves applying the paint composition to the surface of the thermoplastic carrier film by laminar flow coating, followed by drying and then coating and drying each additional layer in sequence to obtain a paint-coated film of excellent gloss and smoothness.
Preferred basecoat and clearcoat compositions for the paint-coated films are polyurethanes. They are especially preferred because of their flexibility and good weather resistance. A problem, however, is that these flexible polyurethane coatings are more susceptible to marring than are harder, rigid thermoset polymers which can be used as clearcoats when flexibility is not required. Marring is an injury to the coating which, though related, is different from scratching. The latter involves cutting into the polymer surface, often times all the way to the substrate. The polyurethanes are resistant to this kind of injury within reasonable limits. Marring on the other hand is the forming of a depression in the polymer surface by contact with a blunt object under conditions not severe enough to cause a scratch. Since basecoat-clearcoat finishes on automobiles, boats and the like are subject to such contacts, improvement in the mar-resistance of flexible paint-coated films of the basecoat-clearcoat type to be used for such purposes is desirable. Furthermore, it is desirable that the mar-resistance be persistent or permanent and not be lost when the finish contacts solvents commonly encountered by automobile finishes.
It is also desirable, while improving mar resistance, to preserve the capability of laminar flow coating, inasmuch as this method of coating is responsible for many of the valuable properties of the new paint-coated films, such as gloss, distinctness of image (DOI) and geometric metamerism (commonly called "flop").
The present invention provides novel paint-coated films having flexible basecoat-clearcoat finishes which have improved resistance to marring and which can be formed by laminar flow coating. The resulting products, hence, have outstanding qualities of gloss, DOI and flop plus improved mar resistance. The layers of the films have good adhesion to each other and the clear layers are free of undesirable haze. Preferred embodiments of the films are thermoformable. They can be stretched up to 100 percent in area and bonded to the contours of three-dimensional substrates by thermoforming without tearing and while retaining gloss and DOI in the stretched areas.